This invention relates to the field of radar signal processors and, in particular, to digital radar signal processors.
Radar systems are often used in security systems to detect the presence of objects intruding into a protected area. The detection of such objects involves the determination of the object's position and velocity.
The position of an object is typically expressed as its distance from the detecting radar system. This distance, or range as it is often called, can be determined from the delay between the transmission of an electromagnetic signal and the receipt of the reflections of that signal off the object. In operation, the area to be scanned by the detecting radar system is divided into a number of range bins. The reflections received by the radar system are periodically sampled, each successive sample corresponding to a more distant range bin, to determine the presence of objects in each range bin.
The velocity of a detected object can be measured from the Doppler frequency shift between the transmitted and received signals. This frequency shift can be used to find the velocity of a detected object with respect to the detection radar system. The determination of the Doppler frequency shift involves the examination of the amount of energy in each of several frequency windows, the examination usually involving either analog or digital filters.
A common way to detect intruding objects using the information received from such a radar system is to gather sampled reflections into a large memory and then to process those samples to determine the velocities of any objects found in the examined range bins.
Such a conventional system is shown schematically in FIG. 1. After electromagnetic pulses are emitted by radar system 101, system 101 samples the reflections from the pulses and the samples are inputted to the memory 120 of processor 110. For a security system examining 50 range bins which requires 100 samples for each range bin, the memory must be capable of storing at least 5,000 sample values. Actually, a memory at least twice that size might be needed to store samples which are being received while the previous 5,000 samples are being processed.
Assuming that 20 different Doppler frequency windows are required to determine the objects' velocities with sufficient precision, then each of the 5,000 samples must pass through 20 Doppler frequency filters (either analog or digital). Thus, to process the 5,000 samples using the system in FIG. 1, 100,000 filter operations would need to take place after all the samples are gathered.
The chief disadvantages of such a system are its requirement of a large memory and the delay between the beginning of a search, which is characterized by the transmission of electromagnetic pulses, and the beginning of the processing of those samples to determine the presence and velocity of any intruding objects.
It is an object of the present invention to simplify the hardware and procedure for processing of radar signals.
It is a further object of the invention to reduce the amount of storage necessary for such radar signal processing.
Yet another object of the present invention is to speed up the radar signal processing to reduce the time between the beginning of a search and the determination of the outcome of a search.